Impeller



R. W. WEEKS July 16, 1935.

IMPELLER Filed Dec. A16, 1932 3mm/m .HUBERT W. WEEKS /M I MW' Patented July 1.6, 1935A f PATENT oFFfl'c'E' Rober: w. weeks, wm cheater, n. applicati@ 1s, 1932, serial No. 647,637 `s (ci. 11o-gist) My invention relates to impellers for transforming the energy of iiuid streams into-mechanical energy or for transforming mechanical energy into the energy of iiuid streams.

5 The invention particularly relates to wind tur- Y bines for driving -power plants.

Anobject of the invention is to provide an impeller of light construction while retaining suili- `cient strength and rigidity to withstand high wind pressures and centrifugal forces.

Another object of my invention is to provide an impeller or blade with is non-corrosive and rust resisting, thereby resulting in a blade having low and constant wind-friction.

Another object of the invention is toprovide a wind turbine. for driving power generating -units for furnishing power to airplane marker Y beacons in isolated sections;the vanes or blades of which are constructed of highly efiicient light '20 renectivaiaateriai soithat the turbine will reilect the silnlightfand serve as daytime markers for the air course.

In sections of the countrrin which -electric power-ioriighting is not easily attainable, it is 25 common.to use storage battery units which' are A charged by generators driven bywind turbines.

To increase. the eiliciency of these turbines it is s essential that the rotating element be aslight as possible, thus reducing unnecessary friction and making the turbine operate on low velocity winds.

decreasing the weight of the4 turbine the suplporting structure ortowerfcanl be made of lighter construction, nd thisresults in a considerable savingincost. Y

Yariousmaterials haveheretofore been usedeto construct impeller blades. Aluminum and aluminum alloys, particularly duralumin, have -not b extensively used.- Many existing impeller units are constructed of .wood. Thseare-solid and 40 not cellular construction. Galvanized sheet iron or steel have been used for impellers of types other than -airfoil ,section and noncellular corr-V struction. I have discovered that stainless-steel with a content of approximately 18% chromiumV neighborhood of .01 or .02 of an inch, the elastic limit of duralumin becomes increasingly small,

55 and, therefore, the ratio of strength to weight o! material.

stainless steel becomesv larger than' for duralumin for such dimensions. In constructing the impeller blade according to my invention I use stainless steel sheets of #28 or #30 D. S. Standard gauge (0.01562 or 0.0125 inches thickness),. 5

thereby permitting a very light fabricated strucin the accompanying drawing, in which:

Figure 1 is a side view of a. single-blade impeller of the type shown in patent to StuartA 1,802,094, made in accordance with my invention;

Figure 2 is an enlarged cross section of Figure 1 along the"lin` 2- 2, showing schematically the manner in which the -blade is built up of sheet surface formed of a number of sheets of stainl less steel I,2, 3, l, 5 and'2a, 3a, 'la and 5a, welded together along their overlapping edges-by spot welding. Suitable sheets of steel 2b, 3b, 4 bfand 5b, formed as channel members extending throughout the length of the blade are arranged 35 at each seam and'tlieir side flanges are welded tothe upper and lower surface sheets topravide .suitable bracing and rigidity to the structure. Cross-bracing channel members fic, 20, 3c.' Qc and 5c, areI `arranged at frequent intervals 40 `between the longitudinal channel members and are spot welded to the surface sheets of the blade. This construction results in a cellular airfoil` section made entirely of sheet'stainless steel. The manner in which the sheets over-lap is shown in Figure 2 where for the sake of clearness, the i sheets are shown without thickness and spaced apart fromeach other. Figure 3 is an enlarged view of a section of Figure v2 showing in detail the arrangement of the surface sheets and the internal bracing members The thickness of the sheets has been greatly exaggerated.

The built-up airtoil blade is secured to a supporting shaft 6 by a hollow shank memberl,

which may be formed of a single sheet of metal in the hub I3 which is provided with the usual blade, with a longitudinal channel member inv using spot welding to secure the elements to# -j ranged so that the trailing edge of one sheet overfolded to form une leadingedge of the shank and the edges welded together along the trailing edge. The shank member is provided with a plurality of finger like extensions 8 engaging both sides of the blade and forming a zigzag edge along which the shank is welded to the blade. This construction aiords more contact surface for the welds and is less liable to rupture than where the welds are formed in a straight line. The shank I is also Yprovided with suitable internal bracing like that of the blade for adding strength and rigidity and for securing the shank to the shaft. It will be understood that the shaft is provided with a hub and is mounted for rotation about an axis, and is counter-weighted on the opposite side of the axis. Where more than one blade is provided, as for example, on a two, three, or multiblade `wind turbine the counter-weight used on the one blade turbine is of course omitted.

In Fig. 4, a multiblade impeller is shown similar to those in common use for pumping water. The blades 9 of the impeller are secured on the inner ends to the ring I0 vand near their outer ends to the ring l I by suitable means. The rings I0 and I I are carried by the spokes l2 secured axle (not shown) and mounted for rotation, The blades 9 are built in airfoil section similar to the bladein Figure 1 except that they -are tapered instead of having a constant width. The manner in which the blades are formed from sheets of stainless steel is schematicallyl shown in Figure 5. The leading edge is formed of a single sheet bent in proper form so that the open edges embrace sheets forming the middle section of the terposed, and the whole is spot welded together. A similar joint is provided between the vmiddle section and the trailing section, and the trailing edge is formed by welding together the edges of the two sheets forming the trailing section.

By taking into consideration the tensile strength, the modulus of elasticity and the specic gravity of various materials, it will be found that the material which I use, stainless steel, offers a saving in Weight of from 6 to 8 times that of galvanized iron and approximately two times that of aluminum. The higher modulus o elasticity as well as the high tensile strength of the stainless steel more than offsets its greater Weight as compared to aluminum and its alloys. On account of its rust resisting properties, stainless steel of very much lighter section can be used as compared with the ordinary galvanized or painted carbon steel. Y

The light weight of the rotating element greatly facilitates starting. The inertia is less andthe devices will start with very much less torque.

While I have indicated that sheets of #28 or #30 gauge are suitableffor constructing my impeller, it will be understood that even thinner gauges may be employed for the skin or surface sheets, and thicker sheets may be used for the self supporting internal bracing and supportingk structure. Also, in the larger blades thicker inaterial may be used near the hub and thinner material towards the tip. I have built and successfully operated a blade of the type shown in Figure 1 having a radius of ten feet, but itis feasible and practical to build blades of this type having a radius as high as 100 to 150 feet. In these larger blades it is possible to use4 sheets of 1A; inch thickness for the internal structure,

gether.

many ways without departing from' the spirit of my invention.

What I claim is:

1. An impeller blade comprising a cellular airfoil section having its skin or outer surface formed of sheet stainless steel of a thickness of the order of 0.0125 inches.

2. An impeller blade comprising a cellular airfoil section formed of sheets of stainless steel spot welded, together and having a thickness f the order of 0.0125 inches.

3. A blade for a wind turbine comprising a cellular airfoil section having a uniform crosssection substantially throughout its length and being formed of sheet stainless steel of a thickness of the order. of 0.0125 inches.

4. An impeller blade comprising a self-supporting skeleton frame having an airfoilsection, and a skin or outer surface' formed of sheet stainless steel of a thickness of the order of 0.0125l inches. l

5. An impeller blade having an air-foil section and provided with a surface formed of a plurality of thin metal sheets extending longitudinally 4Vfof the blade, said sheets being arranged so that lower surfaces of the blade, the flanges of said` channel members being spot welded to the overlapping edges of said surface sheets.'

,6. An impeller blade having an air-foil section and comprising upper and lower surfaces formed of a plurality of thin sheets cf stainless steel extending longitudinally of the blade of a thickness of the order of 0.0125 inches, said sheets being arranged so that the trailing edge of one sheet overlaps the leadingedge of an adjacent sheet, said upper and lower surfaces being joined along the leading edge by a. thin metal sheet bent transversely to fcrm the leading edge of Athe blade, longitudinal bracing channel members arranged Within said blade section and 1ocated between opposite seams formed in the upper and lower surfaces, and the overlapping edges forming said seams being welded together and to the flanges of said channel members.

7. An impeller blade having an airfoil section and comprising upper and lower surfaces formed of a plurality of thin metal sheets extending longitudinally of the blade, said sheets being arranged so that the trailing edge of one sheet overlaps the leading edge of an adjacent sheet,

`said upper and lower surfaces being joined formed of a plurality o-f thin metal sheets of uniform thickness extending substantially the entire length of the blade, said sheets being arvlapsiaheleadmcedzeoiaxxadiacent sbeet,said surfaces. the overlapping eli-les -formlngrsaid vupper and lower surfaces bein: joined alom: tbe seams being welded tosether and to the flanges leading' edge bra thin metal sheet bent'transofsaidcbsnnelmembers, andthetralling edges verscly to ionn tbe leading edge o! the blade, of said upper andlower surfaces being welded to- 5-lonsitudlna1 bracing channel members arranxed :ether to form the trailing edge of the blade. 6

within sald blade section and located een opposite seams farmed mfom upwana lower v. om'r w. WEEKS. 

